JAMA Netw Open
Thiazide diuretics raise hyponatremia risk mainly in older women
Clinical takeaway: When starting thiazides in older adults—especially women ≥80 years—consider early and ongoing sodium monitoring or alternative antihypertensive therapy; routine concern is likely unnecessary in younger patients.
In a large propensity score–matched cohort study of more than 159,000 adults in Sweden, newly initiated thiazide diuretics were associated with a higher risk of hyponatremia compared with calcium channel blockers—but the excess risk was highly dependent on age and sex. Overall, profound hyponatremia (serum sodium <125 mEq/L) occurred in 0.80% of thiazide users vs. 0.46% of calcium channel blocker users during the first two years of treatment. The risk was greatest in women aged ≥80 years, with a cumulative incidence of 2.4% and a number needed to harm of 53 for profound hyponatremia. In contrast, among women younger than 65 years, the absolute risk increase was minimal.
Emphasizing the importance of patient education, the authors note: “If thiazides are prescribed, the patient should be carefully informed about symptoms such as fatigue, confusion, and balance disturbances, which may indicate developing hyponatremia and should prompt seeking immediate medical attention and subsequent sodium concentration analysis.”
Source: Bergh Fahlen C, et al. (2026, March 8). JAMA Netw Open. Thiazides and Risk of Hyponatremia by Age and Sex